Abstract 16825: Brahma Related Gene-1 (BRG1) Protein Mediates Helpful Compensatory Response to Retard Development of Heart Failure

Abstract

Background: Chromatin remodeling can modulate transcription by changing gene accessibility. Brahma Related Gene-1 (Brg1) protein, which is an adenosine triphosphate catalytic subunit that supports chromatin remodeling, has been implicated in development of hypertrophic cardiomyopathy. However, contribution of Brg1 to the development of heart failure (HF) has not been clearly elucidated. Hypothesis: We hypothesize that Brg1 mediates compensatory response to cardiac stress; therefore, loss of Brg1 function will accelerate development of HF. Methods: The myosin light chain-2 Cre/loxP system was used to produce cardiac myocyte specific deletion of Brg1(-/-) mouse model with floxed littermates as control. Results: At baseline, Brg1(-/-) hearts showed mildly reduced left ventricular ejection fraction (LVEF). Aging to 12 months caused LV dilation and further reduction of LVEF in Brg1(-/-). We used trans-aortic constriction (TAC) for pressure overload challenge and chose similarly severe TAC induced pressure gradient as indicated by similarly fast peak flow velocities across the constriction. At 2-weeks post-TAC, Brg1(-/-) hearts exhibited severely reduced LVEF, severely dilated LV, and decreased ability to thicken LV wall during systole. In contrast, control hearts did not dilate and maintained its LVEF with increased LV wall thickness. Thus, Brg1 deletion greatly diminished the heart’s ability to compensate for aging and pressure challenge, thereby accelerating development of heart failure with reduced ejection fraction (HFrEF). Separately, RNA sequence analyses of 12-months aged hearts showed Brg1 deletion caused upregulation of 810 genes including HF associated long noncoding RNA XIST and down regulation of 50 genes, while 3-months old hearts were not significantly different. Conclusion: Brg1 mediates compensatory responses that are helpful to the heart to prevent development of HF; therefore, it is a potential treatment mechanism for HF.